Aviation fuel cold flow additives and compositions

ABSTRACT

Aviation fuel, such as jet fuel, blends and methods for improving cold flow properties of such fuels at extremely low temperatures are disclosed. Cold flow properties of, for example, JP-8 based jet fuels are improved by addition to the fuel of a variety of C 10 -C 16  alkyl poly(meth)acrylate esters and polyvinylesters of C 10 -C 16  alkanoic acids. Demonstratable cold flow improvement of such fuels at temperatures of about −53° C. and below is shown.

FIELD OF THE INVENTION

[0001] The invention pertains to jet fuel blends and methods in which acold flow enhancement agent is added to the jet fuel to improve fuelflow rates and flow characteristics at low fuel temperatures.

BACKGROUND OF THE INVENTION

[0002] It is important that aviation fuel exhibit a freeze point that issufficiently low to allow adequate fuel flow through fuel system linesand filters to the engine. It is known that fuel temperature decreasesas flight time increases and that longer duration flights typicallyrequire lower freezing point fuels than do shorter duration flights.

[0003] Additionally, high altitude flights, such as those conductedunder some military operational conditions, also require lower freezingpoint fuels than do lower altitude conventional flights. Quite obviouslythen, there is a need to provide freeze point depressant/cold flowenhancement aids for aviation fuels, particularly for jet fuels, whichwill allow for sufficient fuel flow to desired combustion locations atthe extremely low fuel temperatures encountered at high altitude andlong duration flights. Publications WO 01/32811 A1 and WO 01/62874 A2discuss details of aviation fuels and the need for lowered freeze pointfuel blends.

[0004] One such means of enhancing the cold flow properties of waxcontaining hydrocarbon fluids is via chemical treatment. For example,use of poly[(meth)acrylates] as a pour point depressant for hydrocarbonlubricating oil is taught by U.S. Pat. Nos. 5,312,884 and 5,368,761.

[0005] WO 01/62874 A2 teaches the use of various chemical additives,including certain copolymers of vinyl acetate and ethylene, to lower thefreeze point of aviation fuels. It is further taught that certainclasses of pour point additives known to those skilled in the art fortreating middle distillates, such as heating oils and diesel fuels, arenot necessarily effective in the treatment of aviation fuel and actuallymay be detrimental.

[0006] U.S. Pat. No. 6,265,360 B1 teaches the use of transesterifiedacrylate polymer to improve the cold flow properties of wax-containingliquid hydrocarbons. It is speculated in the teaching that the additivecan be prepared from a methacrylate and is effective in treating jetfuel. However, the untreated pour point of the responsive fluids waslimited to −40° F. in the teaching and ranged from 75° F.-95° F. in theexamples.

SUMMARY OF THE INVENTION

[0007] Methods for improving the cold flow rate of aviation fuels, andjet fuels in particular, are provided wherein the jet fuel is blendedwith a cold flow rate enhancement agent (CFREA). The CFREA is a polymerhaving a majority of repeat units as follows:

[0008] wherein R₁ is hydrogen, CH₃, or mixtures thereof; R₂ is —C(O)—O—,—O—(O)C—, —C(O)—NH—, or mixtures thereof; and R₃ is chosen from straightand branched C₁₀-C₁₆ alkyl groups. Preferably, the CFREA is apoly[C₁₀-C₁₆ alkyl methacrylate] or a poly[vinylester] of a C₁₀-C₁₆alkanoic acid.

[0009] The invention will be further described in conjunction with theattached drawings and following detailed description.

BRIEF DESCRIPTION OF THE DRAWING

[0010]FIGS. 1 and 2 are graphs showing viscosity of certain test jetfuel/CFREA blends compared to a control sample.

DETAILED DESCRIPTION

[0011] In accordance with the present invention, it has been discoveredthat polymers having the repeat unit (a) as defined below are effectivein depressing (lowering) the pour point of aviation fuel. Repeat unit(a) has the structure:

[0012] wherein R₁ is hydrogen, CH₃, or mixtures thereof; R₂ is —C(O)—O—,—O—(O)C—, —C(O)—NH—, or mixtures thereof; and R₃ is C₁₀-C₁₆ alkyl, ormixtures thereof and the like. Preferably, R₁ is CH₃; R₂ is —C(O)—O—;and R₃ is C₁₀₋₁₂ alkyl, mixtures thereof, and the like. Most preferably,R₁ is CH₃, R₂ is —C(O)—O—, and R₃ is C₁₂ alkyl.

[0013] As used herein, C₁₀-C₁₆ alkyl means any predominantly straightchain alkyl group having 10 to 16 carbon atoms per group. Mostpreferably, the alkyl groups consist of at least 90-mole % straightchain alkyl groups having 10 to 16 carbon atoms per group.

[0014] Exemplary monomers encompassed by the repeat unit (a) include,but are not limited to, alkyl methacrylates such as dodecylmethacrylate, lauryl methacrylate, tridecyl methacrylate, tertradecylmethacrylate, and hexadecyl methacrylate; alkyl acrylates such asdodecyl acrylate, lauryl acrylate, tridecyl acrylate, tertradecylacrylate, and hexadecyl acrylate; N-alkylacrylamide such asN-dodecylacrylamide, N-laurylacrylamide, N-hexadecylacrylamide;N,N-dialkylacrylamide such as N,N-didodecylacrylamide;N-alkylmethacrylamide such as N-dodecylmethacrylamide,N-laurylmethacrylamide, N-hexadecyl-methacrylamide; alkyl vinyl esterssuch as vinyl decanoate and vinyl dodecanoate; and mixtures of any ofthe foregoing and the like.

[0015] The polymers of the present invention may be prepared via methodsknown to those skilled in the art, for example, see Allcock and Lampe,Contemporary Polymer Chemistry, (Englewood Cliffs, N.J., PRENTICE-HALL,1981, chapters 3-5), and U.S. Pat. Nos. 5,312,884 and 5,368,761.Preferably, the polymerization is conducted in a hydrocarbon solventemploying an oil-soluble free radical initiator. The solvent may be anyinert hydrocarbon and is preferably hydrocarbon oil such as Aromatic 100(Exxon), HAN (Heavy Aromatic Naphtha (Exxon), or toluene that iscompatible with the aviation fuel in which the polymer additive is to besubsequently used. Preferred classes of oil-soluble free radicalinitiators include, but are not limited to, the peroxides such aslauroyl peroxide and benzoyl peroxide, and azo compounds such as AIBN(2,2′-azobisisobutyronitrile).

[0016] Any of the conventional chain transfer agents known to thoseskilled in the art may be used to control the molecular weight. Theseinclude, but are not limited to, lower alkyl alcohols such asisopropanol, amines, mercaptans such as n-dodecyl mercaptan andt-dodecyl mercaptan, phosphites such as diethyl phosphite, thiaocids,allyl alcohol, and the like.

[0017] Branching agents known to those skilled in the art may also beused. These branching agents in this case are those compounds having twoor more free radical polymerizable groups that can be either dissolvedor dispersed in hydrocarbon solvent such as Aromatic 100 (Exxon), HAN(Heavy Aromatic Naptha), (Exxon) or toluene that is compatible with theaviation fuel in which the polymer additive is to be subsequently used.Examples of such branching agents include, but are not limited to,methylenebisacrylamide, 1,4-butanediol dimethacrylate, diallylurea,trimethylol propane trimethacrylate, polyethyleneglycol diacrylate, andthe like and may form an optional repeat unit (b). The level ofbranching agent (repeatable unit (b)) utilized is limited to that whichyields oil-soluble or oil-dispersible polymers. More preferably theamount of these branching agents, when used, ranges from about 10 ppm toabout 5 mole % of the total monomer charge.

[0018] It is also known to those skilled in the art that the backbone ofthe polymers compositions of the present invention comprising the repeatunit (a) can optionally be modified to add functionality to vary theirthermal stability. For example, the free radical polymerization can beconducted in the presence of from about 10 ppm to about 20 mole % of2-methylene-1,3-dioxepane to insert ester linkages into the backbone ofthe polymer matrix.

[0019] Thus, an optional repeat unit (c) may also be present in anamount from 0-20 mole %. These repeat units (c) result from free radicalring opening polymerization of a cyclic monomer having the formula:

[0020] wherein R₄ is —O—, —S—, —N(CH₃)—, —CH₂— or mixtures thereof; andx is an integer from about 1 to about 3. Cyclic monomers included withinthis formula are known to undergo thermally initiated radical ringopening polymerization. For example, ring opening of2-methylene-1,3-dioxepane will result in the incorporation of esterfunctionality in the polymer backbone according to the following:

[0021] Accordingly, the polymer may comprise repeat units (a), (b), and(c) wherein (b) when present, is present in an amount of about 10 ppm-5mole % and (c) when present, is present in an amount of 10 ppm to about20 mole %, repeat unit (a) is present in a molar amount of 100% minus(molar amount of (b) and (c))=molar amount (a).

[0022] Alternatively, the polymers of the present invention can beproduced by transesterification of a poly[alkyl(meth)acrylate] bymethods known to those skilled in the art, for example, see U.S. Pat.No. 6,265,360 B1. The starting poly[alkyl(meth)acrylate] is typically ahydrocarbyl acrylate polymer containing from 1 to 10 carbon atoms.Preferably, the starting poly[alkyl(meth)acrylate] would be preparedfrom a (meth)acrylate monomer with relative low cost such as methylacrylate or methyl methacrylate. The alkyl groups are selected primarilywith respect to the boiling point of the corresponding alcohols that areremoved from the reaction mixture in the course of thetransesterification reaction.

[0023] Generally, as the number of carbon atoms increases, the removalof the alcohols creates greater difficulties. The alcohols used fortransesterifying of the starting poly[alkyl(meth)acrylate] includemonohydric alcohols represented by the formula ROH, wherein R is ahydrocarbyl group of about 10 to about 30 carbon atoms. Although bothprimary and secondary alcohols can be used of the transesterificationreaction, primary alcohols are preferred. Most preferred are primaryalcohols having a linear hydrocarbyl structure. The transesterificationreaction may be carried out in the presence of known transesterificationcatalysts. These include acids, bases, and lipase enzymes. The acidsinclude mineral acids, sulfonic acids, as well as mixtures of these. Thebases include alkali metal oxides, hydroxides, or alkoxides. The lipaseenzymes include, but are not limited to, porcine pancreas lipase (PPL)and Novozyme 435. The transesterification reaction can be conducted inthe present of high boiling aromatic or paraffinic solvents.

[0024] As would be understood by one skilled in the art in view of thepresent disclosure, it is intended that the aforementionedpolymerization methods do not in any way limit the synthesis of thepolymer of the present invention. Furthermore, it is to be understoodthat polymers comprising two or more different members from the repeatunit (a) group are also within the purview of the present invention.Preferred CFREA polymers in accordance with the above are thepoly[C₁₀-C₁₆ alkyl(meth)acrylates] and/or polyvinyl esters of C₁₀-C₁₆alkanoic acids.

[0025] The polymers of the present inventions should be added to anaviation fuel, for which improved cold flow performance is desired, inan amount effective for the purpose. In the preferred embodiment of theinvention, the aviation fuel is selected from Jet Fuel A, Jet Fuel A-1,Jet Fuel B, JP-4, JP-8, and JP-8+100. Most preferably the jet fuel is aJP-8 based fuel such as neat JP-8 or the formulated JP-8+100.

[0026] Jet Fuel A and Jet Fuel A-1 are kerosene-type fuels with Jet FuelB being a “wide cut” fuel. Jet A is used for many domestic commercialflights in the U.S. Most preferably, the CFREAs of the invention areused to increase the cold flow characteristics of military jet fuelssuch as JP-5, JPTS, JP-7, JP-8, and JP-8+100. JP-5 is currently used bythe U.S. Navy with JP-8 and JP-8+100 used by the Air Force. These fueltypes are summarized in the following Table 1. TABLE 1 U.S. Military JetFuel Freeze Year Point Intro- ° C. Flash Fuel duced Type Max PointComments JP-5 1952 kerosene −46 60 JPTS 1956 kerosene −53 43 Highthermal stability JP-7 1960 kerosene −43 60 JP-8 1979 kerosene −47 38U.S. Air Force JP-8 + 100 1998 kerosene −47 38 U.S. Air Force, containsadditives for improved thermal stability

[0027] On a 100% actives basis, the CFREA is preferably added to the jetfuel in an amount of about 1-7,500 mg/L of the jet fuel. Morepreferably, the CFREA is added in an amount of between about 250-5,000mg/L, most preferably about 4,000 mg/L, as actives. The jet fuel/CFREAblend is capable of improving the cold flow rate of jet fuel,specifically, JP-8 based jet fuel at fuel temperatures on the order ofabout −53° C. to about −56° C. Experimental results have indicated thatthe CFREAs when blended with JP-8 based jet fuel in accordance with theinvention improve cold flow rates of the fuel so that they are, asmeasured in accordance with Table 2 and the test system described, onthe order of about 0.68 (g/s) and greater at fuel temperatures of about−53° C. to about −56° C.

[0028] The polymers of the invention can be employed in combination withconventional fuel additives such as dispersants, antioxidants, and metaldeactivators. Such additives are known to those skilled in the art, forexample see U.S. Pat. Nos. 5,596,130 and 5,614,081.

[0029] The jet fuel cold flow enhancement agents are preferably used incombination with an adjuvant component comprising an oil-soluble polarnitrogen-containing compound. These are set forth in U.S. Pat. No.4,211,534 (Feldman) incorporated by reference herein. Basically, asstated in the '534 specification, these compounds are oil-soluble aminesalts and/or amides that are generally formed by reaction of at leastone molar proportion of hydrocarbyl acid having 1-4 carboxyl groups ortheir anhydrides with a hydrocarbyl substituted primary, secondary,and/or tertiary amine.

[0030] In the case of polycarboxylic acids, or anhydrides, all of theacid groups may be converted to amine salts or amides, or part of theacid groups may be left unreacted.

[0031] The term “hydrocarbyl” as defined is U.S. Pat. No. 4,211,534includes groups that may be branched or straight chain, saturated orunsaturated, aliphatic cycloaliphatic, aryl, alkaryl, substitutedderivatives thereof and the like. Typically, these hydrocarbyl groupswill consist of from about 4-24 carbon atoms, more preferably 10-20carbon atoms. In general, the resultant compound should containsufficient hydrocarbyl content so as to be soluble in the fuel matrix.

[0032] Exemplary hydrocarbyl substituted acids and anhydrides include,but are not limited to, hexanoic acid, lauric acid, palmitic acid,steric acid, behenic acid, benzoic acids, 1,2,4,5-benzenetetracarboxylicdianhydride, 1,2-cyclohexanedicarboxylic anhydride,ethylenediaminetetraacetic dianhydride, salicylic acid, succinic acid,succinic anhydride, alkenyl succinic anhydrides, polyisobutenyl succinicanhydrides (PIBSA), phthalic acids, phthalic anhydride, naphthenicacids, naphthenic anhydrides, and the like. Particularly preferred isphthalic anhydride.

[0033] The hydrocarbyl substituted amines may be primary, secondary, ortertiary; preferably primary or secondary.

[0034] Exemplary hydrocarbyl substituted primary amines include, but arenot limited to, coco amine, tallow amine, hydrogenated fatty primaryamine, 2-ethylhexylamine, n-dodecyl amine, C₁₂₋₁₄ or C₁₆₋₂₂ tertiaryalkyl primary amines from Rohm and Haas Company marketed under the tradename Primene®, mixtures thereof and the like. Particularly preferred isthe C₁₆₋₂₂ tertiary alkyl primary amine marketed by Rohm and HaasCompany under the trade name Primene® JM-T.

[0035] Exemplary hydrocarbyl substituted secondary amines include, butare not limited to, dicocoalkylamine, didecylamine, dioctadecylamine,ditallowamine, dihydrogenated tallowalkylamine, mixtures thereof and thelike. Particularly preferred is dihydrogenated tallowalkylamine which iscommercially available from Akzo Nobel Corporation under the trade nameArmeen® 2HT.

[0036] As would be understood by one skilled in the art in view of thepresent disclosure, it is intended that the aforementioned examples donot in any way limit the description of the nitrogen-containingcompounds. Furthermore, it is to be understood that ester analogsderived from a hydrocarbyl alcohol, and hydrocarbyl sulfo acid analogssuch as those derived from o-sulphobenzoic acid or its anhydride, asdescribed in European Patent Application No. 0261959, are also withinthe purview of the present invention.

[0037] An especially preferred group of polar nitrogen-containingcompounds is the mixed amine salt/amides derived from reaction ofhydrocarbyl acid (having two or more carboxyl groups) or its anhydridesas set forth above with a hydrocarbyl secondary amine. The resultingintermediate amide acid is then neutralized with a primary amine.

[0038] Generally, the preferred group of polar nitrogen-containingcompounds can be represented by the formula

[0039] wherein Z is a divalent organic radical, R₅ and R₆ and R₇ areindependently chosen from C₁₀-C₄₀ hydrocarbyl groups. The hydrocarbylgroups include straight or branched chain, saturated or unsaturatedaliphatic, cycloaliphatic, aryl or alkylaryl moieties. These hydrocarbylgroups may contain other groups or atoms such as hydroxy groups,carbonyl groups, ester groups, oxygen, sulfur, or chlorine groups. Asstated above, the hydrocarbyl groups may be on the order of C₁₀-C₄₀ withthe range of C₁₄-C₂₄ even more preferred. The R₅, R₆, and R₇ groupingscan also represent mixtures of different hydrocarbyl groups. Preferably,R₇ ≠R₅ or R₆.

[0040] The resulting compound should contain sufficient hydrocarboncontent to be oil-soluble.

[0041] The preferred oil-soluble, polar nitrogen-containing compound isprepared by initial reaction of a hydrocarbyl acid or its anhydride anda secondary amine, such as the Armeen® 2HT. Then, the resulting mixedamine salt/amide is neutralized with a primary amine such as thecommercially available Primene® JM-T product. Approximately equimolaramounts of the reactants are used, resulting in a mixed, substitutedamide/amine salt.

[0042] The most preferred polar nitrogen-containing compound is anoil-soluble mixed amide/amine salt formed via reaction of equimolaramounts of phthalic anhydride with the secondary amine, Armeen® 2HT. Theproduct of this reaction is then further reacted with an equimolaramount of the primary amine, Primene® JM-T to form benzoic acid,2-[(bis(hydrogenated tallow alkyl)amino) carbonyl]-C₁₆-C₂₂ tert-alkylamine salt having the structural formula:

[0043] wherein R₅ and R₆ are mixtures of C₁₆ and C₁₈ hydrocarbon fromthe commercially available tallowamine product, and R₆ is a mixture ofC₁₈₋₂₂ hydrocarbons from the commercially available Primene® JM-Tproduct.

[0044] The adjuvant nitrogen compounds can be used in amounts similar tothose given above in conjunction with CFREA dosage.

[0045] The invention will be described further in conjunction with thefollowing examples that are included for illustrative purposes only andshould not be construed to limit the invention.

EXAMPLE 1 Preparation of Poly[lauryl methacrylate]

[0046] To a 300 ml four-necked reaction flask equipped with a mechanicaloverhead stirrer, thermocouple, reflux condenser, nitrogen sparge tube,addition port with septum and a heating mantle was added laurylmethacrylate (15.0 g, 96% purity), n-dodecyl mercaptan (0.15 g, 1.3% ona molar basis) and toluene (30 ml). The resulting solution was thenheated to 100° C. under nitrogen sparge with mixing. An initiatorsolution comprising AIBN (0.23 g) dissolved in toluene (10 ml) was thenadded to the reactor at a rate of 0.077 ml/min. Upon completion of theinitiator solution addition, the reactor was maintained at 100° C. foran additional two hours before cooling down to room temperature. Theresultant solution was then concentrated in vacuo to remove the toluenesolvent to produce the polymer additive.

EXAMPLE 2 Preparation of Poly[decyl methacrylate]

[0047] To the reactor set-up as described in Example 1 was added decylacrylate (10.0 g, 100% purity), n-dodecyl mercaptan (0.12 g, 1.3% on amolar basis) and toluene (50 ml). The resulting solution was then heatedto 100° C. under nitrogen sparge with mixing. An initiator solutioncomprising AIBN (0.155 g) dissolved in toluene (8 ml) was then added tothe reactor at rate of 0.039 ml/min. Upon completion of the initiatorsolution addition, the reactor was maintained at 100° C. for anadditional two hours before cooling down to the room temperature. Theresultant solution was then concentrated in vacuo to remove the toluenesolvent to produce the polymer additive.

EXAMPLE 3 Preparation of Poly[tridecyl methacrylate]

[0048] To the reactor set-up as described in Example 1 was addedtridecyl methacrylate (15.0 g), n-dodecyl mercaptan (0.16 g, 1.3% on amolar basis) and toluene (26 ml). The resulting solution was then heatedto 100° C. under nitrogen sparge with mixing. An initiator solutioncomprising AIBN (0.3 g) dissolved in toluene (8.7 ml) was then added tothe reactor at a rate of 0.3 ml/min. Upon completion of the initiatorsolution addition, the reactor was maintained at 100° C. for anadditional two hours before cooling down to the room temperature. Theresultant solution was then concentrated in vacuo to remove the toluenesolvent to produce the polymer additive.

EXAMPLE 4 Preparation of Poly[vinyl decanoate]

[0049] To the reactor set up as described in Example 1 was added vinyldecanoate (10.0 g) and toluene (26 ml). The resulting solution was thenheated to 60° C. under nitrogen sparge with mixing. An initiatorsolution comprising AIBN (1.0 g) of dissolved in toluene (50 ml) wasthen added in one shot. Upon completion of the initiator solutionaddition, the reactor was maintained at 60° C. for an additional fourhours before cooling down to the room temperature. The resultantsolution was then concentrated in vacuo to remove the toluene solvent toproduce the polymer additive.

EXAMPLE 5 Preparation of Poly[lauryl methacrylate]

[0050] To the reactor set-up as described in Example 1 was addedAromatic 100 solvent (15.0 g). The resulting solution was then heated to90° C. under a nitrogen sparge with mixing. A monomer solution comprisedof lauryl methacrylate (15.0 grams, 96%), and n-dodecyl mercaptan (1.6grams) and Aromatic 100 solvent (15.0 g) was then added to the reactorat rate of 0.59 ml/min while simultaneously charging an initiatorsolution comprised of lauroyl peroxide (3.6 g) dissolved in toluene (20g) at rate of 0.21 ml/min. Upon completion of the initiator solutionaddition, the reactor was maintained at 90° C. for an additional twohours before cooling down to the room temperature.

EXAMPLE 6 Preparation of Poly[lauryl methacrylate] with a BranchingAgent

[0051] As in Example 5, except the monomer solution also comprised1,4-butanediol dimethacrylate (0.12 g).

EXAMPLE 7 Preparation of Poly[lauryl methacrylate] Inserting an EsterLinkage into the Polymer Backbone

[0052] To the reactor set-up as described in Example 1 was added laurylmethacrylate (14.4 g, 96% purity), 2-methylene-1,3-dioxepane (0.33 g),n-dodecyl mercaptan (0.18 g, 1.3% on a molar basis) and Aromatic 100solvent (25 ml). The resulting solution was then heated to 90° C. undernitrogen sparge with mixing. An initiator solution comprising AIBN (0.31g) dissolved in toluene (12.62 g) was then added to the reactor at arate of 0.15 ml/min. Upon completion of the initiator solution addition,the reactor was maintained at 90° C. for an additional two hours beforecooling down to room temperature.

Example A (Not of the Invention) Preparation of Poly[methyl acrylate]Precursor

[0053] A 2-liter four-necked reaction flask equipped with a mechanicaloverhead stirrer, thermocouple, reflux condenser, nitrogen sparge tube,two additional funnels, and a heating mantle. The first addition funnelwas charged with methyl acrylate (200 g) dissolved in toluene (100 ml).The second addition funnel was charged with benzoyl peroxide (4 g, 97%purity) dissolved in toluene (615 g). The reaction flask was thencharged with 75 g of methyl acrylate monomer solution form the firstaddition funnel and 125 g of benzoyl peroxide solution from the secondaddition funnel. The reaction flask was then slowly heated to 70° C.After maintaining 70° C. for 30 minutes, simultaneous drop-wise additionof the remaining methyl acrylate and benzoyl peroxide solutions wereconducted over a period of 140 and 155 minutes, respectively. During thefeeds an exotherm took place, raising the temperature to 105° C. Uponcompletion of the additions, the reaction temperature set point wasraised to 100° C. Thirty minutes later, a solution of benzoyl peroxide(0.5 g) dissolved in toluene (10 ml) was added to the reaction flask inone portion. After maintaining the reaction temperature at 100° C. foran additional hour, heating was removed. The resultant polymer solutionwas then concentrated in vacuo to remove the toluene solvent to producethe poly(methyl acrylate) precursor.

EXAMPLE 8 Preparation of Transesterified Poly[methyl acrylate]

[0054] To a four-necked reaction flask equipped with a mechanicaloverhead stirrer, thermocouple, reflux condenser, nitrogen sparge tube,Dean-Stark trap and a heating mantle was added of Example A (20 g),toluene (50 ml), ALFOL 1012HA alcohol (29.5 g, a mixture of C₁₀, C₁₂ andC₁₄ alcohols available from Sasol North America), and ISOFOL 14 Talcohol (4.35 g, a mixture of C₁₂, C₁₄, and C₁₆ alcohols available fromSasol North America). The reaction mixture was then heated to 90° C.with stirring. Thereafter, methanesulfonic acid (0.78 g, 70% in water)was added to the reaction mixture in one portion. Forty minutesafterward, the reaction temperature set was raised to 140° C. Aftermaintaining the reaction temperature at 100° C. for an additional fivehours, heating was removed. The resultant polymer solution was thenconcentrated in vacuo to remove the toluene solvent to produce thepoly[alkyl acrylate] additive.

EXAMPLE 9 Preparation of Poly[lauryl methacrylate]

[0055] As in Example 1 except at a larger scale (basis: laurylmethacrylate, 218.2 g, 96% purity).

[0056] The physical characterizations of Examples 1-9 are summarized inTable 2 below. The molecular weights were determined by GPC analysisreferenced to poly[styrene] standards. TABLE 2 Polymer AdditiveCharacterization Monomer Conversion Example (mole %) Mn Mw Mw/Mn 1 94.56900 14700 2.14 2 89.4 3450 6590 1.91 3 87.7 1350 11600 8.58 4 85.1 648034200 5.28 5 96.6 2359 3033 1.29 6 97.8 2116 2991 1.41 7 97.1 7386 111271.51 A 97.8 1500 50400 33.51 8 100.0 14300 104000 7.23 9 94.5 9098 200532.20

[0057] Screening results of the polymeric additive of the presentinvention in the CAST apparatus are provided in Table 3 below. Ingeneral, the CAST apparatus consists of two 500 ml flasks, one atatmospheric pressure and one sealed, connected via a ¼-inch Teflon tube.A known amount of fuel is charged to the flask at atmospheric pressure,and the apparatus is cooled to the desired test temperature in anenvironmental chamber. Once cooled to the desired temperature, vacuum(2-inch Hg) is applied to the sealed flask. The effectiveness of anadditive is determined by measuring the time it takes for the fuel toflow to the sealed flask and the amount of fuel remaining in theatmospheric flask after the fuel flow ceases.

[0058] As shown in Table 3, at approximately −53° C., the untreated fuelhas solidified and exhibited 100% hold up and essentially no fuel flow.Additions of the additive of the present invention to the fueldramatically improved the cold flow properties at approximately −53° C.to −56° C. as evidenced by a substantial decrease in hold up andincrease in fuel flow. TABLE 3 CAST Testing Results in JP-8 Fuel ExampleConc. Fuel Temp Hold up Flow Rate # (mg/L)* (° C.) (%) (g/s) NA −53.5100 NA 1 16000 −53.0 7 1.23 2 16000 −53.2 9 0.95 3 16000 −53.3 6 1.15 416000 −53.0 13 1.03 4 16000 −53.0 18 0.99 5 16000 −55.3 7 1.59 6 16000−56.3 11 1.18 7 16000 −57.2 32 0.83 8 16000 −52.7 6 1.34 8 16000 −53.0 70.88 8 16000 −53.6 7 0.77 8 16000 −52.9 8 0.68 9 16000 −52.9 7 1.26

[0059] Description of the U-2 Wing Simulator Device is provided byErvin, J. S. et al., “Investigation of the Use of JP-8+100 with ColdFlow Enhancer Additives as a Low-Cost Replacement for JPTS”, Energy &Fuels, 13, 1246-1251 (1999). Screening results for the polymericadditive of the present invention in the U-2 Wing Simulator Device aresummarized in Table 4 below. As shown, at approximately −53° C., theuntreated fuel exhibited significant hold-up. Addition of the additiveof the present invention to the fuel dramatically improved the cold flowproperties at approximately −53° C. as evidenced by a substantialdecrease in hold up. TABLE 4 U-2 Wing Simulator Testing Results in JP-8Fuel Initial Final Conc. Tank Weight Weight Hold up Example (mg/L)* Temp(° C.) (lbs) (lbs) (%) NA −49 196.5 192.0 2 NA −52 198.0 107.2 46 916000 −54 201.8 185 8

[0060] When the polymeric CFREAs of the invention are conjointly usedwith an oil-soluble, polar nitrogen-containing compound adjuvant, bothcomponents can be provided in a convenient one drum approach, dissolvedin a suitable organic solvent such as toluent, kerosene, HAN or thelike. The polymeric CFREA is present in such compositions in a molaramount of about 0.01-100 moles polymeric CFREA to about 1.0 moles of thepolar nitrogen-containing compound adjuvant. At present, it is preferredto use the polymeric CFREA, poly[lauryl methacrylate] and polarnitrogen-containing compound detailed in Example 12.

[0061] Additional CFREA polymers and an oil-soluble polar,nitrogen-containing compound used as an adjuvant treatment were preparedand tested as follows:

EXAMPLE 10 Preparation of Poly[lauryl methacrylate]

[0062] To a two-liter four-necked reaction flask equipped with amechanical overhead stirrer, thermocouple, reflux condenser, nitrogensparge tube, addition port with septum and a heating mantle was addedlauryl methacrylate (96%, 218.2 g, 0.823 mole), n-dodecyl mercaptan(98.5%, 2.2 g, 0.01 mole) and toluene (400 ml). The resulting solutionwas heated to 95° C. under nitrogen sparge with mixing. An initiatorsolution consisting of 5.5 grams of 2,2′-azobisisobutyronitrile (AIBN)dissolved in 50 ml of toluene was then added to the reactor at a rate of2.0 ml/min. Upon completion of the initiator solution addition, thereaction was maintained at 95° C. for an additional two hours beforecooling to room temperature. The resultant solution was concentrated invacuo to remove the toluene solvent, then diluted in Aromatic (Exxon)100 to yield a 25 wt % polymer solution (i.e., 25% actives). 95.0%conversion of the monomer was determined by ¹H NMR.

EXAMPLE 11 Preparation of Poly[tridecyl methacrylate]

[0063] To a 300-ml four-necked reaction flask equipped with a mechanicaloverhead stirrer, thermocouple, reflux condenser, nitrogen sparge tube,addition port with septum and a heating mantle was added tridecylmethacrylate (100%, 60.0 g, 0.223 mole), n-dodecyl mercaptan (98.5%, 0.6g, 0.003 mole) and Aromatic 100 (120 ml). The resulting solution wasthen heated to 90° C. under nitrogen sparge with mixing. An initiatorsolution consisting of 1.12 grams of AIBN dissolved in 40 ml of toluenewas then added to the reactor at a rate of 1.1 ml/min. Upon completionof the initiator solution addition, the reaction was maintained at 90°C. for an additional two hours before cooling to room temperature. Theresultant solution was then diluted further with A-100 to yield a 25 wt% active solution. 93.2% Conversion of the monomer was determined by ¹HNMR.

EXAMPLE 12 Preparation of the Nitrogen-Containing Adjuvant CompoundBenzoic acid, 2-[(bis-(hydrogenated tallowalkyl)amino)carbonyl)]-C₁₆₋₂₂-tert alkyl amine salt.

[0064] To a four-necked reaction flask equipped with a mechanicaloverhead stirrer, thermocouple, reflux condenser, nitrogen sparge tube,addition port with septum and a heating mantle was added phthalicanhydride (99%, 5.0 g, 0.03342 mole) and Armeen® 2HT (17.0 g, 0.03342mole amine). The resulting wax mixture was then heated to 90° C. undernitrogen with mixing and held for four hours. Primene® JM-T (10.9 g,0.03342 mole amine) was then added to the reactor at 90° C. over aneight-minute period, after which the batch was maintained at 90° C. foran additional four hours before cooling to room temperature to yield awax like material. This was then diluted in Aromatic 100 to yield a 25wt % solution of the nitrogen-containing compound.

EXAMPLE 13 Preparation of Benzoic acid, 2-[(bis-(hydrogenated tallowalkyl)amino)carbonyl)]-C₁₆₋₂₂-tert alkyl amine salt.

[0065] This preparation was a scaleup of Example 12. To a four-neckedreaction flask equipped with a mechanical overhead stirrer,thermocouple, reflux condenser, nitrogen sparge tube, addition port withseptum and a heating mantle was added phthalic anhydride (99%, 344.74 g,2.30 mole) and Armeen® 2HT (1165.75 g, 2.30 mole amine). The resultingwax mixture was then heated to 90° C. under nitrogen with mixing andheld for one hour. Primene® JM-T (757.51 g, 2.3 mole amine) was thenadded to the reactor at 90° C. over an fifteen-minute period, afterwhich the batch was maintained at 90° C. for an additional one hourbefore adding the Aromatic 100 solvent (6780.36 g) to yield a 25 wt %solution of the nitrogen-containing compound.

[0066] Screening results of the Examples 10-13 additives of the presentinvention in the CAST apparatus are provided in Table 5 below. As can beseen, at approximately −53° C. the untreated fuel has solidified andexhibited 100% holdup and essentially no fuel flow. Addition of theadditives of the present invention as single component treatments to thefuel dramatically improved the cold flow properties at approximately−53° C. as evidenced by a substantial decrease in hold up and increasein fuel flow. In addition, blends of the polymeric CFREA with the polarnitrogen-containing adjuvant compound also exhibited improvement in thecold flow properties of the fuel. TABLE 5 CAST Testing Results in JP-8Fuel Additive Fuel Temp Holdup Flow Additive 1 Additive 2 Ratio Conc.(mg/L)* (° C.) (%) Rate (g/s) None None N/A N/A −53.5 100 N/A Example 10None N/A 8000 −52.7 7 1.38 Example 10 None N/A 16000 −52.9 7 1.26Example 11 None N/A 8000 −53.6 7 1.35 Example 11 None N/A 16000 −53.3 61.15 Example 12 None N/A 8000 −52.7 10 1.34 Example 12 None N/A 16000−53.3 9 0.93 Example 13 None N/A 12000 −57.8 25 0.47 Example 13 None N/A12000 −55.1 7 0.85 Example 13 None N/A 14000 −57.0 13 0.83 Example 13None N/A 14000 −55.2 10 1.06 Example 13 None N/A 16000 −57.1 8 0.82Example 13 None N/A 16000 −55.2 8 0.93 Example 10 Example 12 50/50 6000−53.3 13 1.34 Example 10 Example 12 50/50 16000 −54.8 15 1.50 Example 11Example 12 50/50 6000 −53.1 7 1.50

[0067] Low temperature viscosity studies of the treated fuel werecarried out using a scanning Brookfield Viscometer in the temperaturerange of −5° C. to −60° C. as described by S. Zabarnick and M.Vangsness, Petroleum Chemistry Preprints 2002, 47(3), pp. 243-246(2002). The results of this testing are given in Table 6. As used in thetable, the “knee temperature” is defined as the temperature at which arapid viscosity increase occurs due to crystal formation. It isdesirable to have the knee temperature for a treated fuel to be shiftedto a lower temperature relative to the neat fuel. It is also highlydesirable to minimize the rate of viscosity increase as the fuel iscooled below the knee temperature.

[0068] It can be seen from the data presented in Table 6 that theadditives of the present invention, as either stand alone treatments oras blends of the polymeric CFREA with the nitrogen-containing adjuvantcompound, lower the knee temperature of the fuel. As shown in FIG. 1,blending the additives results in a significant reduction in the rate ofincrease of the viscosity of the fuel compared to use of one of thepolymeric CFREA singly (compare curve “B” to curves “C”, “D”, and “E”).

[0069]FIG. 2 shows that, when the polymeric CFREA is utilized as a standalone treatment, the rate of increase of the fuel are also effected byvarying the molecular weight or use of a branching agent (compare curves“G” and “H” of FIG. 2 to “B” of FIG. 1). In addition, insertion of esterfunctionality into the backbone the polymeric CFREA did not adverselyaffect its cold flow enhancement properties (compare curves “H” of FIG.2 to “B” of FIG. 1).

[0070] The following reference used in FIGS. 1 and 2 show viscosityversus temperature plot data for the following treatments in JP-8 fuel.Letter Additive 1* Additive 2* A None None B 16,000 mg/L Ex. 10 None C12,000 mg/L Ex. 10  4,000 mg/L Ex. 12 D  8,000 mg/L Ex. 10  8,000 mg/LEx. 12 E  4,000 mg/L Ex. 10 12,000 mg/L Ex. 12 F 16,000 mg/L Ex. 5 NoneG 16,000 mg/L Ex. 6 None H 16,000 mg/L Ex. 7 None

[0071] TABLE 6 Low Temperature Viscosity Results - Knee Temperature inJP-8 Fuel Additive Conc. Knee Additive 1 Additive 2 Ratio (mg/L)* Temp(° C.) None None N/A N/A −52.0 Example 10 None N/A 16000 −55.7 Example12 None N/A 16000 −54.0 Example 10 Example 12 50/50 16000 −56.4 Example11 Example 12 50/50 16000 −56.0 Example 5 None N/A 16000 −55.1 Example 6None N/A 16000 −54.9 Example 7 None N/A 16000 −55.5

[0072] While the specification above has been drafted to include thebest mode of practicing the invention as required by the patentstatutes, the invention is not to be limited to that best mode or toother specific embodiments set forth in the specification. The breadthof the invention is to be measured only by the literal and equivalentsconstructions applied to the appended claims.

What is claimed is:
 1. Method of improving the cold flow rate of jetfuel comprising adding to said jet fuel an effective amount for thepurpose of a polymeric cold flow rate enhancement agent (CFREA) having(a) repeat units characterized by the formula

wherein R₁ is hydrogen, CH₃, or mixtures thereof; R₂ is —C(O)—O—,—O—(O)C—, —C(O)—NH—, or mixtures thereof; R₃ is C₁₀-C₁₆ alkyl, ormixtures thereof, repeat units (b) from 0 to 5 mole percent of abranching agent, and (c) from 0 to 20 mole percent of a repeat unitresulting from free radical ring-opening polymerization of a cyclicmonomer characterized by the formula

wherein R₄ is —O—, —S—, —N(CH₃)—, —CH₂— or mixtures thereof; and x is aninteger from 1 to
 3. 2. Method as recited in claim 1 comprising addingfrom a 1-7,500 mg of said CFREA to said jet fuel, based upon 1 liter ofsaid jet fuel.
 3. Method as recited in claim 1 wherein said jet fuel isa JP-8 based jet fuel.
 4. Method as recited in claim 1 wherein saidCFREA is a C₁₀-C₁₆ alkyl poly(meth)acrylate ester.
 5. Method as recitedin claim 1 wherein said CFREA comprises a mixture of C₁₀-C₁₆ alkylpoly(meth)acrylate esters.
 6. Method as recited in claim 1 wherein saidCFREA is a polyvinylester of a C₁₀-C₁₆ carboxylic acid.
 7. Method asrecited in claim 5 wherein said CFREA is poly(vinyldecanoate).
 8. Methodas recited in claim 4 wherein said CFREA is polylauryl(meth)acrylate. 9.Method as recited in claim 4 wherein said CFREA is polydecylacrylate.10. Method as recited in claim 4 wherein said CFREA ispolytridecyl(meth)acrylate.
 11. Method as recited in claim 1 furthercomprising adding, as an adjuvant treatment to said jet fuel about1-7,500 mg/L of an oil-soluble, polar nitrogen compound to said jetfuel.
 12. Method as recited in claim 11 wherein said oil-soluble, polarnitrogen compound comprises an amine salt or amide.
 13. Method asrecited in claim 12 wherein said oil-soluble polar nitrogen compoundcomprises a reaction product formed from reaction of a hydrocarbyl acidhaving two or more carboxyl groups, or anhydride thereof, and ahydrocarbyl secondary amine followed by neutralization of the resultingproduct with a hydrocarbyl primary amine.
 14. Method as recited in claim11 wherein said oil-soluble, polar nitrogen compound is benzoic acid,2-[(bis(hydrogenated tallow alkyl)amino)carbonyl]-C₁₆-C₂₂ tert-alkylamine salt.
 15. Composition for improving the cold flow rate of jet fuelsaid composition comprising, in an organic solvent medium, 1) apolymeric cold flow rate enhancement agent (CFREA) having (a) repeatunits characterized by the formula

wherein R₁ is hydrogen, CH₃, or mixtures thereof; R₂ is —C(O)—O—,—O—(O)C—, —C(O)—NH—, or mixtures thereof; R₃ is C₁₀-C₁₆ alkyl, ormixtures thereof, repeat units (b) from 0 to 5 mole percent of abranching agent, and repeat units (c) having from 0 to 20 mole percentof a repeat unit resulting from free radical ring-opening polymerzationof a cyclic monomer characterized by the formula

wherein R₄ is —O—, —S—, —N(CH₃)—, —CH₂— or mixtures thereof; and x is aninteger from 1 to 3; and 2) an oil-soluble, polar, nitrogen-containingcompound.
 16. Composition as recited in claim 15 wherein 1) is presentin an amount of about 0.01-100 moles of 1) per one mole of 2). 17.Composition as recited in claim 15 wherein said oil-soluble polarnitrogen-containing compound is an amine salt and/or amide. 18.Composition as recited in claim 17 wherein said oil-soluble, polarnitrogen-containing compound is a reaction product formed by reaction ofa C₄-C₂₄ hydrocarbyl acid or anhydride thereof with a C₄-C₂₄ hydrocarbylsubstituted primary, secondary, and/or tertiary amine.
 19. Compositionas recited in claim 18 wherein said oil-soluble, polar nitrogencontaining compound comprises a reaction product formed from reaction ofa hydrocarbyl acid having two or more carboxyl groups or an anhydridethereof and a hydrocarbyl secondary amine followed by neutralization ofthe resulting product with a hydrocarbyl primary amine.
 20. Compositionsas recited in claim 15 wherein said oil-soluble, polar nitrogen compoundis benzoic acid 2-[(bis(hydrogenated tallow alkyl)amino)carbonyl]C₁₆-C₂₂ tert-alkyl amine salt.
 21. Composition as recitedin claim 19 wherein said CFREA is polylauryl(meth)acrylate. 22.Composition as recited in claim 20 wherein said CFREA ispolylauryl(meth)acrylate.